#include "demo11.h"
#include "demo12.h"
#include "demo13.h"
#include <iostream>
#include <string>
#include <ctime>
using namespace std;
void test1()
{
    demo13_inherit demo("hello world", 12, 20, 0.7);
    cout << demo.net_price(12) << endl;
    cout << demo.isbn() << endl;
}
int main()
{
    auto start = clock();
    test1();
    auto end = clock();
    cout << end - start << endl;
    return 0;
}